Graphene is considered a two dimensional structure equivalent to individual graphite sheets or an open carbon nanotube. A single graphene sheet has a theoretical surface area higher than 2500 m2/g, higher than that of activated carbon. However, the term graphene is generally understood to encompass any graphite structure with fewer than about 10 basal plane layers. Basal planes are those layers in which carbon atoms are bound together by covalent bonds.
Graphene's unique properties include: the mechanical strength inherent in the strong covalent bond between adjoining carbon atoms in a basal plane, the potential to organize graphene to create ‘molecular scale’ circuit elements, and the unique chemistry of the ‘edges’ of the graphene sheet. Exemplary applications that use all or some of these properties include: I. Graphene used as gas and bio-sensors, either as pristine, B- or N-doped, due to the dramatic changes on its structural and electronic properties when molecules are absorbed (see Hong et al., J. Phys. Chem. C. 2010 February;114(4): 1822-6; Zhang, et al., Nanotechnology 2009 May; 20(18): 8; and Schedin et al. Nat. Mater. 2007 September; 6(9): 652-5); II. Graphene used as resonator materials due to its thermal conductivity, mechanical properties (e.g., strength and stiffness), and tunable electrical properties (see Frank et al., J. Vac. Sci. Technol. B. 2007 November; 25(6): 2558-61); III. Graphene used as filler material for reinforcing polymers or for generating conductive polymers (see Cho et al., Macromol. Mater. Eng. 2005 March; 290(3): 179-87;Ansari et al., J. Polym. Sci. Pt. B-Polym. Phys. 2009 May; 47(9): 888-97; and Stankovich at al., Nature 2006 July; 442(7100): 282-6). For example, composites made from electrospun polymer nanofibers containing graphene nanoplatelets provide improved Young's modulus (see Viculis et al., J. Mater. Chem. 2005; 15(9): 974-8); and IV. Graphene used for supercapacitor electrodes due to its high electrical conductivity, which improves performance over a wide range of voltage scan rates (see Stoller et al., Nano Lett, 2008 October; 8(10): 3498-502). Additionally, battery, fuel cell and solar cell components based on graphene are an example on how this material is making its way through multiple energy related applications, including both energy generation and storage (see Yong et al., Small. 2010 January; 6(2): 313-8;Liang et al., J. Mater. Chem. 2009; 19(33): 5871-8; Guo et al., ACS Nano. 2010 January; 4(1):547-55; and Liu et al., Advanced Materials. 2008 October; 20(20): 3924).
Conventional methods for producing graphene include chemical vapor deposition (CVD) and related methods that generate graphene free-standing sheets (see Wei et al., Nano Lett. 2009 May; 9(5): 1752-8;and Dato et al., Nano Lett. 2008 July; 8(7): 2012-6), thermal exfoliation of graphite oxide (see McAllister et al., Chem. Mater. 2007; 19: 4396-404; Schniepp et al., J. Phys. Chem. B. 2006 April; 110: 8535-9; and Gass et al., Nat. Nanotech. 2008 November; 3(11): 676-81), and wet chemistry reduction techniques that employ graphite oxide as precursor and liquid reducing agents such as hydrazine and additives to eliminate oxygen group (see Dreyer et al., Chem. Soc. Rev. 2010; 39(1): 228-40; Ju et al., Mater. Lett. 2010 February; 64(3): 357-60;Jung et al., J. Phys. Chem. C. 2008 December; 112(51): 20264-8; Stankovich et al., Carbon 2007; 45: 1558-65;Stankovich et al, J. Mater. Chem. 2006; 16(2): 155-8; and Wang et al., J. Phys. Chem. C. 2008 June; 112(22): 8192-5). However, none of these conventional processes can be readily scaled up to manufacture large quantities of graphene.
Thus, there is a need to develop methods of forming graphene-based products in massive amounts. It is also desirable to provide methods that are rapid, inexpensive, and easy to scale up for forming graphene-based products.